Minimizing Interconnections In A Multi-Shelf Switching System

ABSTRACT

In certain embodiments, minimizing interconnections in a multi-shelf switching system includes receiving a map describing the switching system, where the switching system comprises shelves and input/output (I/O) points. The map is transformed to yield a graph comprising nodes and edges. A node represents an I/O point, and a node weight represents a number of interface cards of the I/O point represented by the node. An edge between a node pair represents traffic demand between the I/O points represented by the node pair, and an edge weight represents the amount of the traffic demand represented by the edge. The graph is partitioned to yield a groups that minimize interconnection traffic among the shelves, where each group represents a shelf of the multi-shelf switching system.

TECHNICAL FIELD

This invention relates generally to the field of switching systems andmore specifically to minimizing interconnections in a multi-shelfswitching system.

BACKGROUND

In a single-shelf switching system, the shelf may be divided into anumber of slots, each of which is able to support an interface card. Astraffic increases, a single-shelf switching system may not have enoughslots to accommodate the increased traffic. The system may useadditional shelves to handle the traffic. The interconnection trafficbetween the shelves, however, may need to be minimized.

SUMMARY OF THE DISCLOSURE

In accordance with the present invention, disadvantages and problemsassociated with previous techniques for organizing multi-shelf switchingsystems may be reduced or eliminated.

In certain embodiments, minimizing interconnections in a multi-shelfswitching system includes receiving a map describing the switchingsystem, where the switching system comprises shelves and input/output(I/O) points. The map is transformed to yield a graph comprising nodesand edges. A node represents an I/O point, and a node weight representsa number of interface cards of the I/O point represented by the node. Anedge between a node pair represents traffic demand between the I/Opoints represented by the node pair, and an edge weight represents theamount of the traffic demand represented by the edge. The graph ispartitioned to yield a groups that minimize interconnection trafficamong the shelves, where each group represents a shelf of themulti-shelf switching system.

In certain embodiments, minimizing interconnections in a multi-shelfswitching system includes receiving a description of the switchingsystem. The switching system comprises shelves and trunks, where thetrunks are organized into trunk pairs and each trunk pair has a trafficdemand. The following is performed for each trunk pair in order ofdecreasing traffic demand and for each shelf in order of decreasingnumber of assigned trunks: a trunk pair is assigned to a shelf if acondition is satisfied in order to minimize interconnection traffic.

Certain embodiments of the invention may provide one or more technicaladvantages. A technical advantage of one embodiment may be that a mapdescribing a multi-shelf switching system may be transformed to yield agraph describing the multi-shelf switching system. The graph may be usedin an optimization problem that partitions the graph into groups. Thegroups represent an assignment of trunks to the shelves of the systemthat may minimize interconnections among the shelves. Another technicaladvantage of one embodiment may be that a technique for assigning thetrunks to the shelves may avoid creating interconnections and mayimprove packing density in order to minimize interconnections.

Certain embodiments of the invention may include none, some, or all ofthe above technical advantages. One or more other technical advantagesmay be readily apparent to one skilled in the art from the figures,descriptions, and claims included herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and itsfeatures and advantages, reference is now made to the followingdescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates an example of a system that is configured to assigntrunks in a multi-shelf switching system;

FIG. 2 illustrates an example of a graph that may be generated accordingto a map of FIG. 1;

FIG. 3 illustrates an example of the graph of FIG. 2 that has beenpartitioned into groups;

FIG. 4 illustrates an example of a method that may be used to partitiona graph in order to assign trunks to shelves; and

FIG. 5 illustrates an example of an optimization problem that partitionsa graph in order to assign trunks to shelves.

DETAILED DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention and its advantages are bestunderstood by referring to FIGS. 1 through 5 of the drawings, likenumerals being used for like and corresponding parts of the variousdrawings.

FIG. 1 illustrates an example of a system 10 that is configured toassign trunks in a multi-shelf switching system. In certain embodiments,system 10 transforms a map describing a multi-shelf switching system toyield a graph describing the multi-shelf switching system. The graph maybe used in an optimization problem that partitions the graph intogroups. The groups represent an assignment of trunks to the shelves ofthe system that minimizes interconnections among the shelves. In certainembodiments, system 10 utilizes a technique for assigning the trunks tothe shelves that avoids creating interconnections and improves packingdensity in order to minimize interconnections.

In the illustrated example, system 10 includes an interface 20, logic24, and a memory 28. Logic 24 includes a processor 30, and applicationssuch as graph generator 34 and trunk assigner 38 stored at memory. Incertain embodiments, system 10 receives a map 14 describing amulti-shelf switching system 30 comprising shelves 38 and input/output(I/O) points, such as trunks and add/drop points 34. System 10 outputsan assignment 18 of points to shelves 38.

To generate assignment 18, system 10 transforms map to yield a graphcomprising nodes and edges that represent the I/O points and trafficdemands between the I/O points, respectively. System 10 partitions thegraph to yield groups that minimize interconnection traffic amongshelves 38, where each group represents a shelf 38 of multi-shelfswitching system 30. System 10 may then output assignment 18 of I/Opoints to shelves 38 based on the groups.

In certain embodiments, multi-shelf switching system 30 comprises aplurality of shelves 38 and a plurality of input/output (I/O) points,such as trunks 32 and add/drop points 34. Examples of multi-shelfswitching systems 30 include reconfigurable optical add-drop multiplexer(ROADM) and electronic network switch systems.

A shelf 38 may have one or more slots, each of which is configured tosupport an interface card. An interface card may be a modular electroniccircuit on a printed circuit board that operates to interface devicesand/or networks. For example, an interface card may operate as aninterface between a computer and a local area network or between a localarea network and a wide area network. An interface card may be able tosupport a certain amount of traffic, such as an amount in one of thefollowing ranges: less than 20, 20 to 40, 40 to 60, or greater than 60G/s gigabits per second (G/s). In the illustrated example, eachinterface card supports 40 G/s of traffic.

An I/O point may be an ingress/egress trunk 32 or an add/droptermination point 34. In certain embodiments, a trunk 32 may be acommunication line between switching systems. An ingress trunk 32 mayreceive traffic at switching system 30, an egress trunk 32 may transmittraffic from switching system 30. A particular trunk 32 may have aswitching capacity for a particular amount of traffic and may requirethe use of a particular number of interface cards. In certainembodiments, “I/O point” may be used interchangeably with “trunk.”

In the illustrated example, trunks 32 of switching system 30 includestrunks A, B, and C. Trunk A has a switching capacity of 60 G/s andrequires two interface cards. Trunk B has a switching capacity of 100G/s and requires four interface cards. Trunk C has a switching capacityof 120 G/s and requires eight interface cards.

In certain embodiments, add/drop termination point adds and/or dropstraffic. An add/drop termination point 34 may have a switching capacityfor a particular amount of traffic and may require the use of aparticular number of interface cards. In the illustrated example,add/drop termination point 34 has a switching capacity of 60 G/s andrequires two interface cards.

Traffic travels through and/or between I/O points, such as trunk pairs.Add/drop traffic travels through an ingress/egress trunk 32 and anadd/drop termination point. Added traffic travels through an add/droptermination point 34 and then an egress trunk 32. Dropped traffictravels through an ingress trunk 32 and then through an add/droptermination point 34. In certain situations, traffic may be groomed at ashelf.

Pass-through traffic travels between ingress/egress trunks 32, or trunkpairs, such as through an ingress trunk 32 and then through an egresstrunk 32. In the illustrated example, the traffic demand between trunksA and B is 20 G/s, between trunks B and C is 10 G/s, between trunks Aand C is 30 G/s, between trunk A and add/drop point is 10 G/s, betweentrunk B and add/drop point is 20 G/s, and between trunk C and add/droppoint is 30 G/s.

In multi-shelf switching system 30, the ingress and egress trunks 32 forpass-through traffic may be on the same or different shelves 38. Ifingress and egress trunks 32 are on different shelves 38, then aninterconnection 36 between the shelves 38 carries the pass-throughtraffic as interconnection traffic.

Different assignments 18 of ingress and egress trunks 32 to shelves 38may result in different amounts of interconnection traffic. In certainsituations, assignments 18 that minimize interconnections 36 may bedesired. Interconnections 36 may require additional interface cards andslots on shelves 38, so minimizing interconnections 36 may reduce thesecosts. In addition, minimizing interconnections 36 may allow for moreinterconnections 36 that can be saved for future growth.

In certain embodiments, map 14 describes the following features of amulti-shelf switching system 30. In the embodiments, map 14 may describethe following: the number of shelves, the number of slots per shelf, thenumber of slots of a shelf reserved for I/O points, the number of slotsof a shelf reserved for interconnections, the capacity of an interfacecard, the number of interface cards that each trunk requires, and/or thetraffic demand for each trunk pair.

In certain embodiments, graph generator 34 transforms map 14 to yield agraph. Trunk assigner 38 partitions the graph to yield groups thatminimize interconnection traffic among the shelves. Each grouprepresents a shelf of the multi-shelf switching system. In certainembodiments, trunk assigner 38 partitions a graph according to anoptimization technique applied to an optimization problem. Generation ofa graph is described in more detail with reference to FIG. 2, andpartitioning the graph is described in more detail with reference toFIG. 3 through 5.

System 10 outputs assignment 18 of trunks to shelves according to thepartitions. Assignment 18 may be output on an output modules of system10 such as a display or printer. In the illustrated example, trunk B isassigned to shelf 2, and trunks A and C are assigned to shelf 1.

FIG. 2 illustrates an example of a graph 40 that may be generatedaccording to map 14 of FIG. 1. Graph 40 comprises nodes 42 and edges 44,where an edge 44 is between a node pair comprising two nodes 42. A node42 represents an I/O point, and a node weight of the node 42 representsa number of interface cards required by the I/O point represented by thenode 42. A node pair may represent traffic, such as pass-through trafficbetween trunks or add/drop traffic between a trunk and add/droptermination point.

An edge 44 between a node pair represents traffic demand between two I/Opoints represented by the node pair, and an edge weight of the edge 44represents the amount of the traffic demand represented by the edge 44.In the embodiments, “node” may be used interchangeably with “I/O point,”“node weight” with “number of interface cards,” “edge” with “trafficdemand,” and “edge weight” with “amount of the traffic demand.”

In the illustrated example, nodes A, B, and C, represent trunks A, B,and C, respectively. Nodes A A/D, B A/D, and C A/D represent add/droppoints for trunks A, B, and C, respectively. The number by a node 42indicates the number of interface cards required by the I/O pointrepresented by the node 42. The number by an edge 44 indicates thetraffic demand of the traffic represented by the edge 44.

FIG. 3 illustrates an example of graph 40 that has been partitioned intogroups 50, such as groups G1 and G2. A group 50 includes nodes 42 andrepresents a shelf 38. In the example, group G1 includes nodes A and Cand represents Shelf 1 of assignment 18. Group G2 includes node B andrepresents Shelf 2.

Trunks represented by nodes 42 of a particular group 50 may be assignedto the shelf 38 represented by the group 50. In the embodiments, “group”may be used interchangeably with “shelf.” In the illustrated example,according to group G1, trunks A and C may be assigned to shelf 1, andaccording to group G2, trunk B may be assigned to shelf 2.

In certain embodiments, graph 40 may be partitioned according to anoptimization technique applied to an optimization problem. For example,the optimization problem may be described as follows.

Objective: Minimize the amount of interconnection traffic betweenshelves of a switching system.

Given:

-   -   K=number of shelves of the switching system    -   S=number of slots per shelf    -   S1=number of slots of a shelf for I/O points    -   S2=number of slots of a shelf for interconnections    -   S1+S2=S    -   M=capacity of an interface card (which may be used for traffic        grooming)    -   For each trunk X, number of interface cards C that trunk X        requires=X(C)    -   For each trunk pair (X,Y), traffic demand D for trunk pair        (X,Y)=(X,Y,D)

Constraints at a Shelf:

1. Number of slots used by I/O points≦S1

2. Number of slots used by interconnections≦S2

The number of shelves K may be determined from the number of requiredslots R and the number of slots per shelf S according to K×S≧R. Thenumber of required slots R may be, for example, the number of slotsrequired by the trunks plus the number reserved for interconnectiontraffic.

In certain embodiments, the optimization problem may be applied to graph40 as follows.

Objective: Partition nodes into K groups such that Min(ΣCut(Gi)).

Given:

-   -   Gi=group i    -   Cut(Gi)=the total weight of edges between Gi and other groups    -   N(Gi)=the total of node weights in Gi

Constraints at a Shelf:

-   -   1. Node weights of I/O points≦S1 N(Gi)≦S1    -   2. Node weights of interconnections≦S2 Cut (Gi)/M≦S2

Given:

Number of groups K=2

Capacity of an interface card M=40

Node weights of shelf S=12,

Node weights of shelf for I/O points S1=10

Node weights of shelf for interconnections S2=2

Example Groups:

G1={A, C, A(A/D), C(A/D)}

G2={B, B(A/D)}

Constraints:

-   -   1. N(G1)=2+8+10/M+30/M=11<S1 N(G2)=4+20/M≈5<S1    -   2. Cut(G1)/M=Cut(G2)/M=30/M=2=S2

Cut(G1)=Cut(G2)=20+10=30

In certain embodiments, the partition problem takes into account nodeweights and/or constraints for node and/or cut weights. In addition, incertain embodiments, the partition problem does not require that thetotal node weight among groups is equal. In certain embodiments, thepartition problem is NP-complete.

As used in particular embodiments, “minimize” generally means to performan optimization that minimizes interconnections. Minimize does not implythat the optimization necessarily yields the absolute minimum number ofinterconnections, although optimization can, in certain cases, yield theabsolute minimum number of interconnections.

FIG. 4 illustrates an example of a method that may be used to partitiona graph 40 in order to assign trunks 32 to shelves 38. The method may beperformed by system 10 of FIG. 1.

In certain embodiments, the method performs the following:

(1) assign a node pair with the highest traffic demand to a group;

(2) if a first node of a node pair has been assigned to a group,assigning a second node of the node pair to the group; and

(3) assigning a node pair to a group with the highest number of assignednodes.

In the embodiments, when the method performs the above steps, the methodmay be regarded as performing the following:

(1) assigning a trunk pair with the highest traffic demand to a shelf;

(2) if a first trunk of a trunk pair has been assigned to a shelf,assigning a second trunk of the trunk pair to the shelf;

(3) assigning a trunk pair to a shelf with a highest number of assignedtrunks.

In certain embodiments, the method operates on trunk pairs (X,Y), whereX represents a first trunk and Y represents a second trunk. The trunkpair has a traffic demand between trunks X and Y. The method starts atstep 210, where trunk pairs are sorted according to traffic demand. Forexample, trunk pairs may be sorted in order of decreasing trafficdemand. If trunk pairs are sorted in this order, a trunk pair with thehighest traffic demand is typically assigned first. A trunk pair isselected in order at step 214.

Shelves are sorted according to the number of trunks assigned to theshelves at step 218. For example, shelves may be sorted in order ofdecreasing number of assigned trunks. In certain embodiments, shelveswith no availability, for example, no available slots, may be omitted. Ashelf is selected in order at step 222.

Steps 226, 230, and 234 may be regarded as assigning the selected trunkpair to the selected shelf if a condition is satisfied. The trunks ofthe selected trunk pair may have already been assigned to the selectedshelf at step 226. For example, in previous iterations, trunk pairs(A,B) and (C,D) may have been assigned to the selected shelf. If theselected trunk pair is (A,D), then the trunks of the selected trunk pairhave already been assigned to the selected shelf.

If the trunks of the selected trunk pair have already been assigned,then the method proceeds to step 228. There may be a next trunk pair atstep 228 that has not been assigned. If there is a next trunk pair, themethod returns to step 214 to select the next trunk pair. Otherwise, themethod proceeds to step 246.

If the trunks of the selected trunk pair have not been assigned at step226, the method proceeds to step 230. A trunk of the selected trunk pairmay have already assigned to the selected shelf at step 230. Forexample, in a previous iteration, trunk pair (A,B) may have beenassigned to the selected shelf. If the selected trunk pair is (A,D),then a trunk of the selected has already been assigned to the selectedshelf. If the trunk of the selected trunk pair has already assigned,then the method proceeds to step 234. Otherwise, the method proceeds tostep 232.

There may be a next shelf of the sorted shelves at step 232. If there isa next shelf, the method returns to step 222 to select the next shelf.Otherwise, the method proceeds to step 242.

Slots of the selected shelf may be available to accommodate the selectedtrunk pair at step 234. Availability of slots may be determined usingthe constraints of the partition problem. For example, slots may beavailable if: (1) the number of available slots is greater than or equalto the number of slots needed to add the trunk pair; and/or (2) thenumber of available interconnection slots is greater than or equal tothe number of interconnection slots needed to add the trunk pair. Thenumber of available slots may be the number of slots that have not beenassigned to an interface card. The number of available interconnectionslots may be the number of reserved interconnection slots that have notbeen assigned. If slots of the selected shelf are available toaccommodate the selected trunk pair, the method proceeds to step 238.Otherwise, the method proceeds to step 232.

The unassigned trunk of the selected trunk pair is assigned to theselected shelf at step 238. The method then returns to step 228 to checkif there is a next trunk pair.

The trunk pair that is unassigned at step 242 is assigned to anysuitable shelf. For example, the trunk pair may be assigned to a shelfthat has the highest number of trunks and that has slots available toaccommodate the trunk pair.

The trunks may be reassigned to different shelves at step 246 to furtherminimize interconnection traffic. The trunks may be reassigned in anysuitable manner. In certain embodiments, a trunk pair may be reassignedfrom a shelf that does not have a common trunk to a shelf that has acommon trunk. For example, trunk pairs (A,B) and (C,D) may be assignedto Shelf 1 and trunk pair (E,F) may be assigned to Shelf 2, which alsohas trunk pair (F, D). Reassigning trunk pair (C,D) from Shelf 1 toShelf 2 may reduce the interconnections.

FIG. 5 illustrates an example of an optimization problem that partitionsa graph 40 in order to assign trunks 32 to shelves 38.

Given:

-   -   Number of slots of shelf S=16,    -   Number of slots of shelf for I/O points S1=12    -   Number of slots of shelf for interconnections S2=4    -   Capacity of an interface card M=2    -   Number of interface cards C that trunk X requires=X(C): A(4),        B(4), C(1), D(1), E(4), F(4), G(2), H(6)    -   For each trunk pair (X,Y), traffic demand D for trunk pair        (X,Y)=(X,Y,D): (A,B,5), (C,D,3), (B,E,3), (E,F,2), (F,D,2),        (G,E,2), (G,H,1)

Constraints at a Shelf:

1. Number of slots used by I/O points≦S1=12. The number of slots used byI/O points may be the sum of interface cards required by the trunksassigned to the shelf, which may be expressed as ΣX_(i)(C_(i)), whereX_(i) is assigned to the shelf.

2. Number of slots used by interconnections≦S2=4. The number of slotsused by interconnections may be the sum of traffic demands of the trunksassigned to the shelf divided by the capacity of an interface card,which may be expressed as ΣX_(i)(D_(i))/M, where X_(i) is assigned tothe shelf.

In the example, the sorted demands are (A,B,5), (C,D,3), (B,E,3),(E,F,2), (F,D,2), (G,E,2), (G,H,1). The trunks are added to shelves inthe following manner.

Trunks A and B are assigned to Shelf 1 at step 210.

ΣX_(i)(C_(i))=4+4=8 for Shelf 1

ΣX_(i)(D_(i))/M= 3/2˜2 for Shelf 1

Number of interconnections: two for Shelf 1

Trunks C and D are assigned to Shelf 1 at step 214.

ΣX_(i)(C_(i))=8+1+1=10 for Shelf 1

ΣX_(i)(D_(i))/M=(3+2)/2˜3 for Shelf 1

Number of interconnections: three for Shelf 1

Trunk E is assigned to Shelf 2 at step 218.

ΣX_(i)(C_(i))=4 for Shelf 2

ΣX_(i)(D_(i))/M=(3+2+2)/2=4 for Shelf 2

Number of interconnections: three for Shelf 1+four for Shelf 2=seven

Trunk F is assigned to Shelf 2 at step 222.

ΣX_(i)(C_(i))=4+4=8 for Shelf 2

ΣX_(i)(D_(i))/M=(3+2+2)/2=4 for Shelf 2

Number of interconnections: three for Shelf 1+four for Shelf 2=seven

Trunk G is assigned to Shelf 2 at step 224.

ΣX_(i)(C_(i))=8+2=10 for Shelf 2

ΣX_(i)(D_(i))/M=(3+2+1)/2=3 for Shelf 2

Number of interconnections: three for Shelf 1+three for Shelf 2=six

Trunk H is assigned to Shelf 3 at step 228.

ΣX_(i)(C_(i))=6 for Shelf 3

ΣX_(i)(D_(i))/M=½˜1 for Shelf 3

Number of interconnections: three for Shelf 1+three for Shelf 2+one forShelf 3=seven

Trunks C and D are reassigned to Shelf 2 at step 228.

ΣX_(i)(C_(i))=10−(1+1)=8 for Shelf 1

ΣX_(i)(D_(i))/M= 3/2˜2 for Shelf 1

ΣX_(i)(C_(i))=10+2=12 for Shelf 2

ΣX_(i)(D_(i))/M=(3+1)/2=2 for Shelf 2

ΣX_(i)(C_(i))=6≦S1 for Shelf 3

ΣX_(i)(D_(i))/M=½˜1 for Shelf 3

Number of interconnections: two for Shelf 1+two for Shelf 2+one forShelf 3=five

Reassigning the trunks decreases the number of interconnections.

A component of the systems and apparatuses disclosed herein may includean interface, logic, memory, and/or other suitable element. An interfacereceives input, sends output, processes the input and/or output, and/orperforms other suitable operation. An interface may comprise hardwareand/or software.

Logic performs the operations of the component, for example, executesinstructions to generate output from input. Logic may include hardware,software, and/or other logic. Logic may be encoded in one or moretangible media and may perform operations when executed by a computer.Certain logic, such as a processor, may manage the operation of acomponent. Examples of a processor include one or more computers, one ormore microprocessors, one or more applications, and/or other logic.

In particular embodiments, the operations of the embodiments may beperformed by one or more computer readable media encoded with a computerprogram, software, computer executable instructions, and/or instructionscapable of being executed by a computer. In particular embodiments, theoperations of the embodiments may be performed by one or more computerreadable media storing, embodied with, and/or encoded with a computerprogram and/or having a stored and/or an encoded computer program.

A memory stores information. A memory may comprise one or more tangible,computer-readable, and/or computer-executable storage medium. Examplesof memory include computer memory (for example, Random Access Memory(RAM) or Read Only Memory (ROM)), mass storage media (for example, ahard disk), removable storage media (for example, a Compact Disk (CD) ora Digital Video Disk (DVD)), database and/or network storage (forexample, a server), and/or other computer-readable medium.

Modifications, additions, or omissions may be made to the systems andapparatuses disclosed herein without departing from the scope of theinvention. The components of the systems and apparatuses may beintegrated or separated. Moreover, the operations of the systems andapparatuses may be performed by more, fewer, or other components. Forexample, the operations of graph generator 34 and trunk assigner 38 maybe performed by one component, or the operations of graph generator 34may be performed by more than one component. Additionally, operations ofthe systems and apparatuses may be performed using any suitable logiccomprising software, hardware, and/or other logic. As used in thisdocument, “each” refers to each member of a set or each member of asubset of a set.

Modifications, additions, or omissions may be made to the method withoutdeparting from the scope of the invention. The method may include more,fewer, or other steps. Additionally, steps may be performed in anysuitable order.

Although this disclosure has been described in terms of certainembodiments, alterations and permutations of the embodiments will beapparent to those skilled in the art. Accordingly, the above descriptionof the embodiments does not constrain this disclosure. Other changes,substitutions, and alterations are possible without departing from thespirit and scope of this disclosure, as defined by the following claims.

1. A method comprising: receiving a map describing a multi-shelfswitching system, the multi-shelf switching system comprising aplurality of shelves and a plurality of input/output (I/O) points;transforming the map to yield a graph comprising a plurality of nodesand a plurality of edges, a node representing an I/O point, a nodeweight of a node representing a number of interface cards of the I/Opoint represented by the node, an edge between a node pair representingtraffic demand between the I/O points represented by the node pair, anedge weight of an edge representing the amount of the traffic demandrepresented by the edge; and partitioning the graph to yield a pluralityof groups that minimize interconnection traffic among the shelves, eachgroup representing a shelf of the multi-shelf switching system.
 2. Themethod of claim 1, the I/O points comprising one or more ingress/egresstrunks and one or more add/drop termination points.
 3. The method ofclaim 1, the partitioning the graph further comprising: assigning a nodepair with the highest traffic demand to a group.
 4. The method of claim1, the partitioning the graph further comprising: if a first node of anode pair has been assigned to a group, assigning a second node of thetrunk node to the group.
 5. The method of claim 1, the partitioning thegraph further comprising: assigning a node pair to a group with thehighest number of assigned nodes.
 6. One or more computer readablestorage media encoded with computer code when executed by a processorconfigured to: receive a map describing a multi-shelf switching system,the multi-shelf switching system comprising a plurality of shelves and aplurality of input/output (I/O) points; transform the map to yield agraph comprising a plurality of nodes and a plurality of edges, a noderepresenting an I/O point, a node weight of a node representing a numberof interface cards of the I/O point represented by the node, an edgebetween a node pair representing traffic demand between the I/O pointsrepresented by the node pair, an edge weight of an edge representing theamount of the traffic demand represented by the edge; and partition thegraph to yield a plurality of groups that minimize interconnectiontraffic among the shelves, each group representing a shelf of themulti-shelf switching system.
 7. The computer readable storage media ofclaim 6, the I/O points comprising one or more ingress/egress trunks andone or more add/drop termination points.
 8. The computer readablestorage media of claim 6, the computer code configured to partition thegraph by: assigning a node pair with the highest traffic demand to agroup.
 9. The computer readable storage media of claim 6, the computercode configured to partition the graph by: if a first node of a nodepair has been assigned to a group, assigning a second node of the trunknode to the group.
 10. The computer readable storage media of claim 6,the computer code configured to partition the graph by: assigning a nodepair to a group with the highest number of assigned nodes.
 11. A methodcomprising: receiving a description of a multi-shelf switching systemcomprising a plurality of shelves and a plurality of trunks, the trunksorganized into trunk pairs, each trunk pair having a traffic demand; andperforming the following for each trunk pair in order of decreasingtraffic demand: performing the following for each shelf in order ofdecreasing number of assigned trunks: assigning the each trunk pair tothe each shelf if a condition is satisfied in order to minimizeinterconnection traffic.
 12. The method of claim 11, the assigning theeach trunk pair further comprising: if the each trunk pair has thehighest traffic demand, assigning the trunk pair to the each shelf. 13.The method of claim 11, the assigning the each trunk pair furthercomprising: if a first trunk of the each trunk pair has been assigned tothe each shelf, assigning a second trunk of the each trunk pair to theeach shelf
 14. The method of claim 11, the performing the following foreach trunk pair further comprising: if the each trunk pair has not beenassigned, assigning the each trunk pair to a shelf with the highestnumber of assigned trunks.
 15. The method of claim 11, the assigning theeach trunk pair further comprising: assigning the each trunk pair to theeach shelf only if the each shelf has availability for the each trunkpair.
 16. The method of claim 11, further comprising: reassigning theassigned trunks to further minimize the interconnection traffic.
 17. Oneor more computer readable storage media encoded with computer code whenexecuted by a processor configured to: receive a description of amulti-shelf switching system comprising a plurality of shelves and aplurality of trunks, the trunks organized into trunk pairs, each trunkpair having a traffic demand; and perform the following for each trunkpair in order of decreasing traffic demand: perform the following foreach shelf in order of decreasing number of assigned trunks: assign theeach trunk pair to the each shelf if a condition is satisfied in orderto minimize interconnection traffic.
 18. The computer readable storagemedia of claim 17, the computer code configured to assign the each trunkpair by: if the each trunk pair has the highest traffic demand,assigning the trunk pair to the each shelf.
 19. The computer readablestorage media of claim 17, the computer code configured to assign theeach trunk pair by: if a first trunk of the each trunk pair has beenassigned to the each shelf, assigning a second trunk of the each trunkpair to the each shelf
 20. The computer readable storage media of claim17, the computer code configured to perform the following for each trunkpair by: if the each trunk pair has not been assigned, assigning theeach trunk pair to a shelf with the highest number of assigned trunks.21. The computer readable storage media of claim 17, the computer codeconfigured to assign the each trunk pair by: assigning the each trunkpair to the each shelf only if the each shelf has availability for theeach trunk pair.
 22. The computer readable storage media of claim 17,the computer code configured to: reassign the assigned trunks to furtherminimize the interconnection traffic.